Primary biliary cirrhosis (PBC) and autoimmune hepatitis (AI-CAH) are two chronic diseases of the liver, believed to be autoimmune in nature, with etiologies and pathogenesis that remain unknown. These disorders affect predominantly women, mostly in the prime of their life. For example, over 90% of patients with PBC are women between the ages of 20-70. Liver transplantation has proven to be an effective treatment for both AI-CAH and PBC. However, disease recurrence remains an important concern. The goal of this project is to elucidate the role of cytokines and cytotoxic mediators in autoimmune liver disease. Specifically, we propose to: 1) characterize the cytokine profiles within the liver of patients with PBC and AI-CAH 2) identify the cytotoxic mediators 3) characterize the functional properties of lymphoid cells that have infiltrated the liver and 4) apply this information to establish immunological parameters that distinguish disease recurrence from allograft rejection. Molecular methodologies will be utilized to determine and compare the cytokine arrays in normal liver and liver explant tissue from patients with PBC and AI-CAH. RNA obtained from liver tissue will be reverse transcribed, and analyzed for cytokine gene expression using semi- quantitative PCR. In situ hybridization and immunohistochemical techniques will identify the cellular source of cytokine message within the liver. evidence for specific cellular pathways of liver tissue injury will be obtained by immunohistochemical techniques and Western blot hybridization analysis for serine esterases, perforin, eosinophil cytotoxic proteins and autoantibodies. Direct in vitro examination of infiltrating cells recovered from the PBC and AI-CAH liver will establish the diversity of T cells within the infiltrate, the cytotoxic activity and specificity of T lymphocytes, the frequency of specific cytokine producing cells, the arrays of intrahepatic autoantibodies, and the presence of non-specific effector cells including NK cells and eosinophils. The effect of recombinant cytokines on MHC antigen expression by target tissue will be tested on epithelial and hepatocyte-derived cell lines. Finally, patterns of cytokine production in PBC and AI-CAH will be compared with these of- patients who have received liver transplants because of autoimmune liver disease in an effort to distinguish disease recurrence from allograft rejection. Taken together, these studies will provide important mechanistic insights into these two enigmatic autoimmune diseases as well as clarify the issue of disease recurrence post-orthotopic transplantation.